Hovering Hawkmoths Slow Their Brains to See at Night and Track Robot Flowers

Scientists are learning a bit more about the amazing night vision of hovering hawkmoths. Researchers have taken a closer look at these hummingbird-sized moths to find out what obstacles they have to overcome while feeding on nectar at night.

In this latest study, the researchers used high-speed infrared cameras and 3D printed robotic flowers to see what occurs when this insects flits from flower to flower.

"There has been a lot of interest in understanding how animals deal with challenging sensing environments, especially when they are also doing difficult tasks like hovering in mid-air," said Simon Sponberg, one of the researchers, in a news release. "This is also a very significant challenge for micro air vehicles."

Researchers already knew that moths use specialized eye structures to maximize the amount of light they can capture. Yet they also wondered if the moths had any other unusual features that allowed them to better hover in place while feeding at night.

The researchers found that the moths could track robotic flowers that were oscillating at rates of up to 20 hertz, which is two oscillations per second. This is considerably faster than the two-hertz maximum seen in real flowers. Because moths' wings beat at about 25 strokes per second, they had to adjust their movement at every wingstroke.

"This is really an extreme behavior, though the moth makes it look simple and elegant," said Sponberg. "To maneuver like this is really quite challenging. It's an extreme behavior from both a sensory and motor control perspective."

The researchers also found that the moths slow the activity of their brains to focus and improve their vision under low-light conditions while still performing demanding tasks.

"This was an interesting example of how an organism can tune its brain to maintain its ability to gather food," said Sponberg. "The moths do suffer a trade-off by slowing their brains, but that trade-off doesn't end up mattering because it only affects their ability to track movements that don't exist in the natural way that flowers blow in the wind."